1. Field of the Invention
The present invention relates to a compressed video decoder. More specifically, the present invention relates to a compression-based reduced memory video decoder, with substantially lossless compression.
2. Description of the Related Art
The most popular video encoders in present use utilize motion compensated prediction, followed by transmission of a compressed error signal, as a means of efficient compression. Some encoders use forward prediction (past reference), while other decoders use both forward and backward (future reference) prediction. The standard MPEG-1 and MPEG-2 class of video encoders use both of these two types of predictions.
The implication for a video decoder is that it must maintain a copy of these reference pictures in order to decode the picture that referenced them. An MPEG decoder, for example, must have sufficient memory to store the decoded version of at least two reference pictures, in addition to a display buffer consisting of the current picture being decoded and displayed.
A standard MPEG-2 video decoder includes a channel buffer, a variable length decoder (VLD), an inverse quantization (IQ) means, an inverse discrete cosine transform (IDCT) means, a motion compensator, an anchor frame storage, and a display memory.
In the related device, the total memory space includes memory to store incoming coded data, channel buffer, and sufficient memory in anchor frame storage to store at least two reference pictures, in addition to the display memory.
Requiring this amount of memory is disadvantageous, because memory space is expensive and accounts for the largest percentage of the cost of a video decoder.